Experience with Lumin L2?

It's going to be impossible for anyone to say.
The only way to find out for sure would be to get a home demo from a dealer or owner, so that you can listen to it in your exact setup and compare.

Even if I was confident in an improvement, putting a value of $4000 on it is entirely subjective, especially as you have a system you already like and is already addressing some of the problems that L2 aims to fix.

Just received and installed the L2 in my system; it was an instant upgrade. Music flows more easily and with greater separation and detail compared to my previous setup listed below.  I agree with Wojciech Pacula (High Fidelity, Poland) who said it works best as a combined library and switch. Keeping everything within the Lumin ecosystem (I have an X1) has tangible benefits. Chris Connaker of Audiophile Style came to the same conclusion.

Prior to using the L2 as a switch, I had an etherRegen switch with an attached AfterDark OCXO clock with digital filter and digital cable and linear power supply.  All that is now gone.

I was also accessing my stored music via a Synology NAS and, as a secondary approach, SSDs inside a Roon NUC.

I’m using all the network ports on the L2: fiber from my router and fiber to the X1. The RJ45 connections are to the Roon NUC and a TV.

Now, I mainly use the JPlay for iOS app to play music through my X1, specifically Tidal streaming and stored music on two 2TB Samsung SSDs that I installed without a hitch.  I rarely use my Roon setup, preferring it primarily for music discovery.

Great to hear. Thanks for the feedback!